At present, it is known that titanium dioxide (TiO2) nanoparticles, which are used as a main material of a UV-screening agent, have a better UV-screening effect when the size of the titanium dioxide nanoparticles is smaller. UV-screening ingredients are contained in commercially available skin care creams and lotions, makeup foundations, BB creams, and even in lip balms. However, when a lotion, for example, that contains titanium dioxide nanoparticles is rubbed on the skin burned by the sun or damaged by acne, the titanium dioxide nanoparticles may enter the human body through the skin to have harmful effects on the human body. Moreover, it is reported that the titanium dioxide nanoparticles are harmful materials to the human body through animal tests, and the National Institute for Occupational Safety and Health (NIOSH, USA) proposes a dose limit (0.1 mg/m2).
Therefore, a method for reducing side effects, which may be caused by the titanium dioxide nanoparticles used as an active ingredient of the UV-screening agent, has attracted much attention.
Meanwhile, halloysite is a material represented by Al2Si2O5(OH)4.2H2O and is an aluminum silicate clay mineral having a ratio of aluminum to silicon of 1:1. The halloysite is a nano-sized plate type and has a layer structure in which different layers are alternately layered in a ratio of 1:1. Moreover, the halloysite is naturally present in aluminosilicate. The outer surface of the halloysite comprises a silicate SiO2− layer, and the inner surface comprises an alumina Al2O3+ layer. The halloysite has a hollow nanotubular structure, in which the inner diameter is about 30 to 250 nm and the length is about 0.2 to 0.4 μm and thus has excellent carrier characteristics. Moreover, the halloysite is a natural mineral harmless to the human body, and thus there are no environmental problems and no harm to the human body. As a result, the nano-sized tubular halloysite has unique properties as a carrier and thus has been used as a container for an active substance, i.e., a carrier for delivering a fragrance, cosmetic, drug, etc.
However, it has not been reported that a hybrid powder in which light-scattering nanoparticles are loaded into halloysite nanotubes is developed.
Therefore, it is believed that when the light-scattering nanoparticles are loaded into halloysite nanotubes and used as an UV-screening agent, it is possible to reduce or eliminate side effects occurring on the skin. Thus, the need to develop a hybrid powder in which light-scattering nanoparticles are loaded into halloysite nanotubes is urgently required.